Process for heating stamped metal discs

ABSTRACT

A process for heating stamped metal discs or other plates, or rings, having radially extending tongues, prior to the forming of the stamped blanks into spring retainer members and the like, the process comprising electrically connecting together the tongues of a stamped blank at or near their free ends, and then heating the stamped blank to a predetermined desired temperature by electrical induction heating. The process may be carried out with the stamped blank supported in a press which is used to deform and quench the blank subsequent to it being heated to the predetermined temperature. The press accommodates a contact ring for electrically connecting the tongues under pressure and means for rotating the stamped blank during the induction heating of the blank.

[111 3,737,609 [451 June 5, 1973 [54] PROCESS FOR HEATING STAMPED METAL DISCS [75] Inventor: Franz Josef Overkott, Gevelsberg,

Germany [73] Assignee: Firma Paul Ferd. Peddinghaus,

Gevelsberg, Germany [22] Filed: Aug. 24, 1971 [21] Appl. No.: 174,435

[30] Foreign Application Priority Data Feb. 16, 1971 Germany ..P 21 07 355.2

[52] US. Cl. "219/1041, 219/1057, 219/1073,

[56] References Cited UNITED STATES PATENTS Jagen.. ..219/10.41 x

6/1944 Limpel ..2l9/lO.41X 6/1955 Ireland ..2l9/l0.4lX

Primary Examiner-J. V. Truhe 4ssisrqnt E. aminerB. A. Reynolds Attorney- David Toren and Bernard X. McGeady [5 7] ABSTRACT A process for heating stamped metal discs or other plates, or rings, having radially extending tongues, prior to the forming of the stamped blanks into spring retainer members and the like, the process comprising electrically connecting together the tongues of a stamped blank at or near their free ends, and then heating the stamped blank to'a predetermined desired temperature by electrical induction heating. The process may be carried out with the stamped blank supported in a press whichis used to deform and quench the blank subsequent to it being heated to the predetermined temperature. The press accommodates a contact ring for electrically connecting the tongues under pressure and means for rotating the stamped blank during the induction heating of the blank.

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PROCESS FOR HEATING STAMPEI) METAL DISCS Spring discs, spring plates, spring retainer plates, re-

silient retainer rings and the like, are commonly manufactured from stamped metal plates or rings having radially extending projections or tongues. The stamped blanks are heated and then deformed, if necessary, between dies in a press and simultaneously quenched. The heating is usually carried out by passing the stamped blanks slowly through a travelling hearth furnace, and subsequently, the deformed and quenched products are assembled together in stacks and tempered to give them the desired spring properties. However, this method has certain disadvantages. In the first place heating the stamped blanks in a travelling hearth furnace is a very slow process. Besides being uneconomic, this tends to promote the formation of coarse grains in the blank which can spoil the surface finish. Furthermore the temperatures in a furnace of this kind are unevenly distributedand consequently the stamped blanks cannot be heated asevenly as is desirable. A still further disadvantage of travelling hearth furnaces is that they occupy a great deal of space. Many attempts have been made to use induction heating instead of the cumbersome and uneconomic travelling hearth furnace to heat the stamped blanks. However, it has hitherto not been possible to obtain a satisfactorily even heating of the stamped blanks by an induction heating method, due to the characteristic construction of the blanks, which consist of an annular or other shaped part with radially extending projections or tongues. Attempts have been made to apply a perfectly uniform heating to the stamped blanks by using inductors of special shape and by rotating the blanks during the heating, but success has not been achieved, even with inductors which produce a very flat, almost quadratic alternating electric field, the blanks being made to travel through the alternating field. Nor has success been obtained by using kidney shaped, square or asymmetric inductors, with or without concentrators.

We have now found, however, that simply by shortcircuiting the radially extending tongues by connecting them together, induction heating may be used to heat the stamped blanks to the desired uniformity. Therefore, according to the present invention, we propose a process for heating a stamped metal plate or ring having radially extending tongues, in which the tongues are electrically connected together at or near their free ends and the stamped blank is heated to the desired temperature by electrical induction heating. By appropriately constructing the arms of the inductor used to effect the heating, a transverse electric field is induced in the stamped blank which produces an evenly distributed heating, in spite of the different cross sections at different parts of the blank. The induced transverse field is limited in extent by the shape of the inductor, but apart from this limitation the induced field can be given almost any desired shape. It is desirable to use an inductor with an ohmic resistance as low as possible, keeping the coupling gap also as small as possible. With the process in accordance with the invention stamped blanks of the kind described can be heated very rapidly obtaining a very satisfactory even distribution of temperatures. This helps to provide a very rapid method of manufacturing spring plates and rings etc.

Preferably the tongues are connected together electrically by means of a contact ring which is held under pressure against the tongues, and best results are obtained if the blank is rotated during the induction heating. This provides an extremely even temperature distribution throughout the blank and the product has an extremely fine crystalline structure.

If the heated products are to be made into spring members, it is convenient if the stamped blank is rotated and heated while being supported in a press which is subsequently used both for deforming and for quenching the heated blank. The blank may be rotated at a speed of between 50 and 500 revs/minute. In the press the stamped blanks are first of all evenly heated and then, after the desired temperature is reached, they are automatically deformed and simultaneously quenched.

In order to obtain a still more rapid manufacturing process the temperature of the blank is measured by a 'pyrometer with direct contact with the blank and without any time delay. As soon as the measured temperature reaches the desired value, the deformation and quenching is automatically initiated.

According to a further feature of the invention apparatus for use in the process comprises an electrical inductor for induction heating the stamped blank, and a contact ring for electrically connecting together the radially extending tongues of the stamped blank by an arrangement of concentric conductors.

The apparatus may include a press for deforming and for quenching the blank after it has been heated, the press accommodating the contact ring so that the ring can connect the tongues while the blank is supported in the press.

Preferably the contact ring is carried by an axial thrust bearing and is axially movable in the press into and out of driving engagement with a centering plunger, there being drive means for rotating the centering plunger.

The apparatus may be used in the fully automatic manufacture of spring members from the stamped blanks, the blanks being fed cold to the press, for example, by pneumatic and/or magnetic feeding and delivering devices.

An example of a method and of apparatus in accordance with the invention will now be described with reference to the accompanying diagrammatic drawings, in which:

FIG. 1 is a plan view of a stamped blank from which a spring disc is to be formed;

FIG. 2 shows an inductor and a concentriccontact ring for use in heating the blank;

FIG. 3A is a sectional view through a press, with a die and a counter die in spaced relationship arranged for use in conjunction with the parts shown in FIG. 2, and

FIG. 3B is a view similar to FIG. 3A with the die and counter die moved together for working on the blank.

As shown in FIG. 1, the stamped blank 4 which is to be deformed and hardened is circular with an outer annular part 5 from which there project radially inwards a number of projections or tongues 6. An inductor 7, note FIGS. 2, 3A and 3B is provided for heating the stamped blank 4. The inductor 7 has two arms 8 and 9 which are arranged to extend over and under the blank 4 as shown in FIGS. 2 and 3A. In order to heat the entire blank, consisting of the outer annular part 5 and the radially inwardly projecting tongues 6, evenly throughout, the tongues 6 are short circuited, i.e., electrically connected together, at their inner ends 11 by a concentric contact ring 12. In operation, the two inductor arms 8 and 9 act in conjunction with the contact ring 12 to produce an induced transverse electric field capable of heating the entire blank evenly through to a temperature which is determined by the generator output and by the-shape of the inductor.

In order to improve the uniformity of temperature distribution over the entire blank 4, the contact ring 12, together with the blank 4, is rotatably driven about the common axis. For this purpose the contact ring 12 is connected, as shown in FIG. 3A, to a centering plunger 13, which is rotatable in the direction indicated by the arrow by a driving mechanism 30. The contact ring 12 is supported from its upper surface by an axial thrust bearing 14, the arrangement allowing the contact ring 12 to be held under pressure axially in contact with the inner ends 1 1 of the tongues-6 of the blank 4, while also allowing the ring and the blank to be rotated. As shown in FIG. 3A, the contact ring 12, the centering plunger 13 and the axial thrust bearing 14 are all accommodated by and operate in a press 15, which is arranged to deform and quench the blank 4 after it has been heated. That is to say, the blank 4 is heated while supported by the press and is then deformed and also quenched in the press 15. The press has an upper or counter die 16 and a lower die 17, containing channels l8, 19 extending in an axial direction and annular grooves 20 in their cooperating faces 21, 22, for the passage of quenching fluid. The lower surface 21 of the upper die 16 and the upper surface 22 of the lower die 17 form mating conical surfaces which, either by a downward movement of the upper die 16 or by an upward movement of the lower die 17, or by a combination of these two movements, deform the blank 4 to the desired conical shape as soon as the stamped blank has been heated to the desired temperature. The temperature of the stamped blank is measured by means of a pyrometer 23, which measures the temperature without contacting the blank and without any appreciable time delay. The pyrometer is connected to a control system 32, and, in turn, the control system is connected to cylinder 24 joined by a disc 25 to the thrust bearing 14.

The blank shown in FIG. 1 is deformed and hardened, that is to say converted into the finished product, by the following procedure:

With the contact ring 12 in a raised position a stamped blank 4 is fed into position on the lower die 17. The contact ring 12 is moved downwards by the cylinder 24 and is thrust, through the axial thrust bearing 14, into firm contact with the upper surface of the blank 4 at the inner ends of the tongues 6, the ring 12 is disposed concentrically about the axis of the blank and acts to center the blank 4 on the lower die 17. The inductor 7 is advanced inwards over and under the blank 4, and electric power supplied to the inductor produces an even alternating electric field which, in conjunction with the contact ring 12, heats the blank 4 evenly throughout. During the heating process the blank 4 is rotated by the centering plunger 13, which is coupled to the contact ring 12, at a speed between 50 and 500 revs/minute. During the heating of the blank 4 its temperature is measured by the pyrometer 23. As soon as the temperature of the blank has reached the desired deformation temperature, the inductor 7 is retracted out of the way. The pyrometer signals and control system 32 and the upper die 16 is moved downwards, or the lower die 17 is moved upwards, so that the blank is deformed between the two dies, quenching fluid being introduced simultaneously under pressure through the channels 19, and flowing from one groove to the other through the spaces between the tongues 6 before leaving through the channels 18. At the same time the cylinder 24 lifts or removes the contact ring 12 from the blank. The quenching process is controlled to give the deformed blank a hard martensite structure.

Alternatively, if desired, the quenching fluid can be introduced through the channels 18 and leave the system through the channels 19. However, whichever direction is used, the arrangement is particularly effective in producing the desired hardness in the metal product. At least one of the two dies 16 and 17, prefer ably both, is water cooled. The best quenching fluid to use depends on the material from which the blank is made. The quenching fluid may be air, a cooling fog, water, oil or an emulsion. However, the best quenching fluid has been found to be air, because the product remains clean and no subsequent cleaning process is necessary.

The invention is, of course, not limited to the particular example just described. In particular the blank need not necessarily be circular. It may have any shape, provided that it has radial projections or tongues. The tongues may project radially inwards or radially outwards. The inductor and the dies may have other shapes and be arranged in other ways. The hardening process may be controlled either automatically or manually, the best method depending on the hardening temperature.

I claim:

1. A process of heating a stamped metal blank comprising a body part and a plurality of tongues projecting radially from said body part, said process consisting of the steps of providing said stamped blank, providing electrical connection means, electrically connecting together said tongues of said stamped blank at or near the free ends of said tongues with said electrical connection means, providing electrical induction heating means and heating said stamped blank to a predetermined desired temperature with said electrical induc- I tion heating means.

2. A process as claimed in claim 1, wherein said electrical connection means is a contact ring, and said ring is held under pressure against said tongues.

3. A process as claimed in claim 1, including the step of rotating said stamped blank during said induction heating of said blank.

4. A process as claimed in claim 3, wherein said blank is rotated at a speed of between 50 and 500 rpm.

5. A process as claimed in claim 3, including the step of providing a press for deforming and quenching said blank subsequent to said blank being heated to said predetermined temperature, and wherein said blank is supported in said press during said simultaneous heating and rotating steps.

6. A process as claimed in claim 5 including the steps of continuously measuring the temperature of said stamped blank directly and without contacting said blank, and automatically triggering said press to deform and quench said blank when said predetermined temperature is reached.

7. Apparatus for heating a stamped metal blank including a body part and a plurality of tongues projecting radially from said body part and said body part and said tongues disposed concentrically about the axis of said blank, comprising an electrical conductor for induction heating said metal blank, and a contact ring arranged to be disposed concentrically about the axis of said blank for electrically connecting together the radially extending tongues of said stamped blank.

8. Apparatus as claimed in claim 7, including a press for deforming and for quenching said stamped blank after it has been heated, a stamped blank supporting surface in said press, and means in said press for accommodating said contact ring whereby said ring can connect said tongues while said blank is supported on said blank supporting surface.

9. Apparatus as claimed in claim 8, including an axial thrust bearing, said contact ring being connected to to said axial thrust bearing, a centering plunger in said press, drive means for rotating said centering plunger, and means mounting said axial thrust bearing and said contact ring for axial sliding movement in said press into and out of driving engagement with said centering plunger.

10. Apparatus as claimed in claim 9, wherein said press includes a die and a counter die, and said centering plunger is mounted centrally in said die.

11. Apparatus as claimed in claim 10, wherein said die and counter die are provided with cooperating faces each of which defines an annular groove surrounding the axis of said die and counter die, and means defining ducts which extend in the axial direction through said die and counter die and communicate with said grooves.

12. Apparatus as claimed in claim 7, including a pyrometer for measuring the temperature of said stamped blank without contact and with substantially no time delay. 

1. A process of heating a stamped metal blank comprising a body part and a plurality of tongues projecting radially from said body part, said process consisting of the steps of providing said stamped blank, providing electrical connection means, electrically connecting together said tongues of said stamped blank at or near the free ends of said tongues with said electrical connection means, providing electrical induction heating means and heating said stamped blank to a predetermined desired temperature with said electrical induction heating means.
 2. A process as claimed in claim 1, wherein said electrical connection means is a contact ring, and said ring is held under pressure against said tongues.
 3. A process as claimed in claim 1, including the step of rotating said stamped blank during said induction heating of said blank.
 4. A process as claimed in claim 3, wherein said blank is rotated at a speed of between 50 and 500 r.p.m.
 5. A process as claimed in claim 3, including the step of providing a press for deforming and quenching said blank subsequent to said blank being heated to said predetermined temperature, and wherein said blank is supported in said press during said simultaneous heating and rotating steps.
 6. A process as claimed in claim 5 including the steps of continuously measuring the temperature of said stamped blank directly and without contacting said blank, and automatically triggering said press to deform and quench said blank when said predetermined temperature is reached.
 7. Apparatus for heating a stamped metal blank including a body part and a plurality of tongues projecting radially from said body part and said body part and said tongues disposed concentrically about the axis of said blank, comprising an electrical conductor for induction heating said metal blank, and a contact ring arranged to be disposed concentrically about the axis of said blank for electrically connecting together the radially extending tongues of said stamped blank.
 8. Apparatus as claimed in claim 7, including a press for deforming and for quenching said stamped blank after it has been heated, a stamped blank supporting surface in said press, and means in said press for accommodating said contact ring whereby said ring can connect said tongues while said blank is supported on said blank supporting surface.
 9. Apparatus as claimed in claim 8, including an axial thrust bearing, said contact ring being connected to to said axial thrust bearing, a centering plunger in said press, drive means for rotating said centering plunger, and means mounting said axial thrust bearing and said contact ring for axial slidinG movement in said press into and out of driving engagement with said centering plunger.
 10. Apparatus as claimed in claim 9, wherein said press includes a die and a counter die, and said centering plunger is mounted centrally in said die.
 11. Apparatus as claimed in claim 10, wherein said die and counter die are provided with cooperating faces each of which defines an annular groove surrounding the axis of said die and counter die, and means defining ducts which extend in the axial direction through said die and counter die and communicate with said grooves.
 12. Apparatus as claimed in claim 7, including a pyrometer for measuring the temperature of said stamped blank without contact and with substantially no time delay. 